Why is insertion sort stable

In the last post we looked at how to really understand Bubble Sort by solving it on paper, one step at a time. We'll take the same approach for Insertion Sort. As with most fundamental sorting algorithms, the chances of this showing up in a FAANG interview is minimal. The one curious case when you should implement this algorithm is when you're asked to sort a collection Online , that is as you receive each element. Given an unsorted array of integers, we want to sort them in ascending order.

The array under consideration is shown below:. Again, this is the most important part to understand in this article. It's not the code or the analysis, but solving it on paper. If you can do this, everything else will be a piece of cake. Note: I'd highly recommend that you try this on paper - this'll help you really understand the insertion sort algorithm and remember it in the long term. Also, this is good practice for explaining the algorithm to your interviewer on a whiteboard.

The worst case is when the entire array is sorted in descending order. Can we make any sorting algorithm stable? Any given sorting algo which is not stable can be modified to be stable. There can be sorting algo specific ways to make it stable, but in general, any comparison based sorting algorithm which is not stable by nature can be modified to be stable by changing the key comparison operation so that the comparison of two keys considers position as a factor for objects with equal keys.

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Change Language. Related Articles. Table of Contents. Save Article. Improve Article. Like Article. Next Time Complexities of all Sorting Algorithms. Recommended Articles. Find the Minimum length Unsorted Subarray, sorting which makes the complete array sorted. Article Contributed By :. The state of array after the loops are finished- With each loop cycle, One element is placed at the correct location in the sorted sub-array until array A is completely sorted. Time Complexity Analysis- Selection sort algorithm consists of two nested loops.

Owing to the two nested loops, it has O n 2 time complexity. It performs all computation in the original array and no other array is used. Hence, the space complexity works out to be O 1. Important Notes- Insertion sort is not a very efficient algorithm when data sets are large. This is indicated by the average and worst case complexities. Insertion sort is adaptive and number of comparisons are less if array is partially sorted.

Time Complexity.